Silver-loaded nanofluorine-doped bismuth titanate and method for preparing the same

Abstract

The application provides a silver-loaded nanometer fluorine-doped bismuth titanate, which is prepared by loading silver nanoparticles on nanometer fluorine-doped bismuth titanate. As a photocatalyst for degrading organic pollutants, the silver-loaded nanometer fluorine-doped bismuth titanate has good stability, can be recycled, and has a service life effectively prolonged as a photocatalyst, and is beneficial to application in actual production.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, specifically relating to a silver-supported nano-fluorine-doped bismuth titanate and its preparation method. Background Technology

[0002] Water is an indispensable resource for humankind, but global industrial development has severely damaged water bodies with toxic pollutants. The development of industries such as papermaking, textiles, leather, dyeing, printing, and plastics, and the resulting wastewater discharge of dyes into the environment, have extremely adverse effects on the ecological environment and human health. Scientists are using photocatalysis, a "green technology," to study how to solve industrial pollution problems and eliminate pollutants in the aquatic environment. In photocatalytic reactions, semiconductors are generally used as catalysts. When exposed to light with energy greater than the semiconductor's bandgap, electrons undergo transitions and partially transfer to the catalyst surface, resulting in a redox reaction that converts pollutants into environmentally friendly substances. In sunlight, ultraviolet light, visible light, and near-infrared light account for approximately 5%, 48%, and 47%, respectively. Therefore, finding catalysts with high visible light utilization has always been a research hotspot.

[0003] As a representative of multi-component Ti-based oxides (BTO), due to its layered structure and unique electronic structure, it possesses an internal electric field along the

[001] direction between the (001) planes. This facilitates the migration of photogenerated electron-hole pairs, making it a highly attractive photocatalyst with excellent thermal stability. Substitution of Ti with metal ions... 4+ While elemental doping is the primary method for improving visible light absorption, the introduction of nonmetallic elements into perovskite structures has received little attention. However, doping with nonmetallic ions can also adjust the bandgap, improve visible light absorption, and enhance photogenerated charge separation efficiency.

[0004] Metal loading is considered one of the most effective means of promoting carrier separation and migration, especially the use of noble metals. In addition to expanding the visible light absorption region due to the surface plasmon resonance (SPR) effect, it can not only promote the migration of interfacial carriers by utilizing the constructed Schottky junction, but also act as an electron trap to accelerate the efficient separation of carriers.

[0005] Therefore, by modifying the catalyst through element doping, surface defects, heterojunctions, etc., the visible light absorption region can be expanded, the recombination rate of charge carriers can be reduced, and the charge separation and transport efficiency can be improved, thereby increasing the degradation rate of pollutants. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a silver-supported fluorine-doped bismuth titanate nanoparticle, prepared by loading silver nanoparticles with fluorine-doped bismuth titanate. After fluorine doping and silver loading, the photocatalytic activity is significantly improved due to the synergistic effect of both, and the lifespan of the photocatalyst is effectively extended, which is beneficial for its application in practical production.

[0007] The purpose of this invention is to provide a silver-loaded nano-fluorine-doped bismuth titanate, which is prepared by loading silver nanoparticles with nano-fluorine-doped bismuth titanate.

[0008] The present invention also aims to provide a method for preparing silver-loaded nano-fluorine-doped bismuth titanate, wherein the method involves adding nano-fluorine-doped bismuth titanate to a solvent containing a silver compound and preparing it through a solvothermal reaction.

[0009] The method specifically includes the following steps:

[0010] Step 1. Prepare fluorine-doped titanium dioxide;

[0011] Step 2. Fluorine-doped titanium dioxide and bismuth compounds are added to the reaction solvent and reacted at high temperature in a sealed environment to obtain nano-fluorine-doped bismuth titanate;

[0012] Step 3. Add nano-fluorine-doped bismuth titanate to a solvent containing silver compounds and perform a solvothermal reaction to obtain silver-loaded nano-fluorine-doped bismuth titanate.

[0013] Another object of the present invention is to provide the use of the silver-supported nano-fluorine-doped bismuth titanate as a photocatalyst for the catalytic degradation of organic pollutants, such as methyl orange and / or methylene blue. The degradation efficiency of organic pollutants is higher than 95 wt%.

[0014] The silver-supported nano-fluorine-doped bismuth titanate provided by this invention has the following beneficial effects:

[0015] (1) In this invention, bismuth titanate with silver loading and fluorine doping was prepared. The synergistic effect of the two improved the carrier separation efficiency and photoelectric conversion efficiency, further promoted the degradation of pollutants, and was beneficial to improving the degradation efficiency and degradation rate of organic pollutants.

[0016] (2) The silver-supported nano-fluorine-doped bismuth titanate provided by the present invention has high photocatalytic activity, good stability, and can be used repeatedly, and its service life is significantly improved. In the actual pollutant degradation process, it is beneficial to reduce the cost of catalyst.

[0017] (3) The preparation method of silver-loaded nano-fluorine-doped bismuth titanate provided by the present invention is simple and the conditions are easy to control. The loading of silver nanoparticles in silver-loaded nano-fluorine-doped bismuth titanate increases the separation efficiency of photogenerated carriers and prolongs the lifetime of photogenerated charges. More holes migrate to the catalyst surface and participate in the degradation of organic pollutants such as methyl orange and methylene blue, thereby improving the degradation efficiency. Attached Figure Description

[0018] Figure 1 (a) shows a TEM image of Ag / tBTO in Comparative Example 1 of the present invention; Figure 1 (b) and Figure 1 (c) HRTEM images of different positions of Ag / tBTO in Comparative Example 1 of the present invention are shown respectively;

[0019] Figure 2 (e) shows a TEM image of Ag / 0.25F-tBTO in Example 1 of the present invention; Figure 2 (f) shows the HRTEM image of Ag / 0.25F-tBTO in Example 1 of the present invention;

[0020] Figure 3 The TEM-EDS mapping scan of Ag / 0.25F-tBTO in Embodiment 1 of the present invention is shown.

[0021] Figure 4 The XRD patterns of 0.25F-tBTO, Ag / 0.25F-tBTO in Example 1 and tBTO, Ag / tBTO in Comparative Example 1 are shown.

[0022] Figure 5 Raman spectra of 0.25F-tBTO, Ag / 0.25F-tBTO in Example 1 and tBTO, Ag / tBTO in Comparative Example 1 are shown.

[0023] Figure 6 (a) shows the degradation efficiency curves of methyl orange in the presence of 0.25F-tBTO, Ag / 0.25F-tBTO, tBTO, and Ag / tBTO; Figure 6 (b) shows the fitted curve obtained by kinetic fitting of the photodegradation of methyl orange according to the first-order reaction formula ln(C0 / C)=kt; Figure 6 (c) shows the degradation efficiency curves of methylene blue in the presence of 0.25F-tBTO, Ag / 0.25F-tBTO, tBTO, and Ag / tBTO; Figure 6 (d) shows the fitting curve obtained by kinetic fitting of the methylene blue photodegradation according to the first-order reaction formula ln(C0 / C)=kt;

[0024] Figure 7(a) shows the degradation efficiency curves of methyl orange solution after three cycles of Ag / tBTO and Ag / 0.25F-tBTO. Figure 7 (b) shows the degradation efficiency curves of Ag / tBTO and Ag / 0.25F-tBTO for methylene blue solution after three cycles;

[0025] Figure 8 (a) shows the transient photocurrent response spectra of 0.25F-tBTO, Ag / 0.25F-tBTO, tBTO, and Ag / tBTO; Figure 8 (b) Shows the EIS Nyquist curves for 0.25F-tBTO, Ag / 0.25F-tBTO, tBTO, and Ag / tBTO;

[0026] Figure 9 The fluorescence spectra of 0.25F-tBTO, Ag / 0.25F-tBTO in Example 1 and tBTO, Ag / tBTO in Comparative Example 1 are shown.

[0027] Figure 10 The surface photovoltage spectra of 0.25F-tBTO, Ag / 0.25F-tBTO in Example 1 and tBTO, Ag / tBTO in Comparative Example 1 are shown. Detailed Implementation

[0028] The present invention will now be described in detail through specific embodiments, and the features and advantages of the present invention will become clearer and more explicit with these descriptions.

[0029] This invention provides a silver-loaded fluorine-doped bismuth titanate nanoparticle, which is prepared by loading silver nanoparticles with fluorine-doped bismuth titanate nanoparticles.

[0030] The present invention also provides a method for preparing the silver-supported nano-fluorine-doped bismuth titanate, wherein the method involves adding nano-fluorine-doped bismuth titanate to a solvent containing a silver compound and preparing it by a solvothermal reaction.

[0031] The method specifically includes the following steps:

[0032] Step 1. Prepare fluorine-doped titanium dioxide.

[0033] The fluorine-doped titanium dioxide is obtained by adding fluorides and titanium compounds to a solvent, reacting them in a solvothermal manner, and then calcining.

[0034] The fluoride is selected from inorganic fluorides, preferably ammonium fluoride.

[0035] The titanium compound is selected from one or more of titanate compounds and titanate ester compounds, preferably one or more of titanate ester compounds, and more preferably one or more of tetrabutyl titanate, tetraisopropyl titanate and tetraethyl titanate.

[0036] The solvent is selected from one or more alcohol solvents, preferably from alkanols containing 1-4 carbon atoms, and more preferably from one or more of ethanol, propanol, n-butanol and isopropanol, such as anhydrous ethanol.

[0037] Preferably, dilute nitric acid is also added to promote the dissolution of the raw materials.

[0038] The molar ratio of the fluoride to the titanium compound is (0.05-2.2):1, preferably (0.15-1.5):1, more preferably (0.25-0.75):1, such as (0.6-0.7):1. Wherein, the fluoride is defined by the molar amount of fluorine, and the titanium compound by the molar amount of titanium.

[0039] The volume molar ratio of the solvent to the titanium compound is (15-45) mL:0.01 mol, preferably (20-40) mL:0.01 mol, and more preferably (25-35) mL:0.01 mol. The titanium compound is defined by the molar amount of titanium in it.

[0040] The solvothermal reaction temperature is 130-230℃, preferably 150-210℃, more preferably 170-190℃, and the reaction time is 12-32h, preferably 15-28h, more preferably 18-24h. The solvothermal reaction is carried out in a closed reaction vessel.

[0041] The product exhibits good photocatalytic performance at reaction temperatures between 150 and 210℃. The optimal photocatalytic performance is achieved at 180℃.

[0042] When the reaction temperature is 180℃, the photocatalytic performance of the product is lower than that of the product when the solvothermal reaction time is 12-15h, and the photocatalytic performance is optimal when the reaction time is 18-24h.

[0043] After the solvothermal reaction is completed, the solvent is removed, and the product is washed and dried to obtain a solid product. After calcining the solid product, fluorine-doped titanium dioxide is obtained.

[0044] The calcination temperature is 400-500℃, preferably 420-480℃, more preferably 440-460℃, and the calcination time is 1.5-4.5h, preferably 2-4h, more preferably 2.5-3.5h.

[0045] The photocatalytic activity of the product obtained by calcination at 400-420℃ is lower than that obtained by calcination at 420-480℃. Among them, the product synthesized at a calcination temperature of 450℃ has the best photocatalytic performance.

[0046] When the calcination temperature is 450℃ and the calcination time is 1.5-2h, the product obtained has lower photocatalytic activity than the product obtained when the calcination time is 2-4h. Among them, the synthesized product obtained by calcination for 3h has the best photocatalytic performance.

[0047] Step 2. Fluorine-doped titanium dioxide and bismuth compound are added to water and reacted at high temperature in a sealed environment to obtain nano-fluorine-doped bismuth titanate.

[0048] The bismuth compound is a water-soluble or acid-soluble bismuth-containing compound, preferably a water-soluble bismuth salt, more preferably one or more of bismuth nitrate, bismuth nitrate pentahydrate and bismuth ammonium citrate, such as bismuth nitrate and / or bismuth nitrate pentahydrate.

[0049] The mass molar ratio of the fluorine-doped titanium dioxide to the bismuth-containing compound is 1 g:(0.005-0.40) mol, preferably 1 g:(0.01-0.30) mol, and more preferably 1 g:(0.015-0.20) mol.

[0050] The mass-to-volume ratio of the fluorine-doped titanium dioxide to water is 0.1g:(4-28)mL, preferably 0.1g:(6-20)mL, and more preferably 0.1g:(8-12)mL.

[0051] The method further includes the addition of a surfactant selected from one or more of alcohols, alkyl quaternary ammonium salts, polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP), preferably selected from one or more of ethanol, glycerol, polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP), and more preferably PVP.

[0052] The mass ratio of the surfactant to fluorine-doped titanium dioxide is 0.03:(0.01-0.2), preferably 0.03:(0.05-0.15), and more preferably 0.03:(0.1-0.12).

[0053] The method also includes the addition of an aqueous mineralizing agent, selected from one or more alkaline substances, preferably from one or more alkali metal hydroxides, and more preferably from NaOH and / or KOH.

[0054] The concentration of the mineralizing agent aqueous solution is 2.5-7.5 mol / L, preferably 3.5-6.5 mol / L, and more preferably 4.5-5.5 mol / L.

[0055] The molar ratio of the mineralizer to fluorine-doped titanium dioxide is (0.1-0.4) mol:0.1 g, preferably (0.15-0.35) mol:0.1 g, and more preferably (0.2-0.3) mol:0.1 g.

[0056] The reaction temperature is 130-230℃, preferably 150-210℃, more preferably 170-190℃, and the reaction time is 12-32h, preferably 15-28h, more preferably 18-24h.

[0057] Step 3. Add nano-fluorine-doped bismuth titanate to a solvent containing silver compounds and perform a solvothermal reaction to obtain silver-loaded nano-fluorine-doped bismuth titanate.

[0058] The silver compound is selected from one or more silver salts, preferably from one or more silver halides, silver nitrates and silver sulfates, and more preferably from silver nitrates.

[0059] The molar ratio of the silver compound to nano-fluorine-doped bismuth titanate is 0.01 mmol:(0.2-0.8) g, preferably 0.01 mmol:(0.3-0.7) g, and more preferably 0.01 mmol:(0.4-0.6) g.

[0060] The solvent is selected from one or more alcohol solvents, preferably from one or more of methanol, ethanol, propanol, isopropanol and n-butanol, and more preferably anhydrous ethanol.

[0061] The volume-to-mass ratio of the solvent to nano-fluorine-doped bismuth titanate is 10 mL:(0.4-0.9) g, preferably 10 mL:(0.5-0.8) g, and more preferably 10 mL:(0.6-0.7) g.

[0062] The solvothermal reaction is carried out in a closed reaction vessel. The reaction temperature is 130-230℃, preferably 150-210℃, more preferably 170-190℃, and the reaction time is 6-18h, preferably 8-16h, more preferably 10-14h.

[0063] After the reaction was completed, the sample was washed and dried to obtain silver-supported nano-fluorine-doped bismuth titanate.

[0064] This invention also provides the use of the silver-supported nano-fluorine-doped bismuth titanate as a photocatalyst for the catalytic degradation of organic pollutants, such as methyl orange and / or methylene blue. The degradation efficiency of organic pollutants is higher than 95 wt%.

[0065] The silver-supported fluorine-doped bismuth titanate nanoparticles provided by this invention can be used as a photocatalyst for degrading organic pollutants, exhibiting good stability and recyclability. After fluorine doping and silver loading, the photocatalytic activity is enhanced due to the synergistic effect of both. The loading of Ag nanoparticles can increase the catalyst's absorption intensity of visible light and improve the separation efficiency of photogenerated carriers, promoting the migration of photogenerated holes to the catalyst surface. Simultaneously, the lifespan of the photocatalyst is effectively extended, which is beneficial for its application in practical production.

[0066] Example

[0067] Example 1

[0068] 0.25 g of ammonium fluoride was added to 30 mL of anhydrous ethanol. After stirring for 30 minutes, 3.4 g of tetrabutyl titanate was added. While stirring, 1 mL of nitric acid (68 wt%) and 1 mL of deionized water were slowly added. The mixture was sealed in a 50 mL polytetrafluoroethylene liner and heated to 180 °C in an oven for 20 h. The product was washed three times with deionized water and ethanol, and dried at 60 °C for 15 h. After cooling to room temperature, it was ground into powder. The powder was then calcined in a muffle furnace at a programmed heating rate of 5 °C / min to 450 °C for 180 min to obtain 0.25F-TiO2.

[0069] 0.1 g of 0.25F-TiO2 was added to 10 mL of deionized water and sonicated for 20 min. Then, 0.03 g of polyvinylpyrrolidone (PVP) and 0.84 g of bismuth nitrate pentahydrate were added, and the mixture was transferred to a 100 mL polytetrafluoroethylene (PTFE) liner. 50 mL of 5 mol / L NaOH solution was added, and the mixture was stirred continuously at room temperature for 60 min. The reaction vessel was sealed and placed in an oven at 180 °C for 18 h. After cooling to room temperature, the sample was washed twice with deionized water and anhydrous ethanol, and dried at 60 °C for 12 h to obtain nano-fluorine-doped bismuth titanate 0.25F-tBTO.

[0070] 0.68 g of 0.25F-tBTO was placed in a beaker, and 0.002 g of silver nitrate and 10 mL of anhydrous ethanol were added. The mixture was stirred for 60 min, then placed in an autoclave with a polytetrafluoroethylene liner, sealed, and heated at 180 °C for 12 h. After cooling to room temperature, the filtered solid sample was washed twice each with deionized water and anhydrous ethanol, and dried at 60 °C for 12 h to obtain Ag / 0.25F-tBTO nanopowder.

[0071] Comparative Example

[0072] Comparative Example 1

[0073] Add 3.4 g of tetrabutyl titanate to 30 mL of anhydrous ethanol. While stirring, slowly add 1 mL of nitric acid (68 wt%) and 1 mL of deionized water. Transfer the mixture to a 50 mL polytetrafluoroethylene-lined container and heat in an oven to 180 °C for 20 h. The resulting product is washed three times with deionized water and ethanol, and dried at 60 °C for 15 h. After cooling to room temperature, grind into powder. Calcine in a muffle furnace at a programmed heating rate of 5 °C / min to 450 °C for 180 min to obtain TiO2.

[0074] 0.1 g of TiO2 was sonicated in 10 mL of deionized water for 20 min. Then, 0.03 g of polyvinylpyrrolidone (PVP) and 0.84 g of bismuth nitrate pentahydrate were added, and the mixture was transferred to a 100 mL polytetrafluoroethylene (PTFE) liner. 50 mL of 5 mol / L NaOH solution was added, and the mixture was stirred continuously at room temperature for 60 min. The mixture was then placed in an oven and heated at 180 °C for 18 h. After cooling to room temperature, the sample was washed twice with deionized water and anhydrous ethanol, and dried at 60 °C for 12 h to obtain nano-bismuth titanate (tBTO).

[0075] 0.68 g of tBTO was placed in a beaker, and 0.002 g of silver nitrate and 10 mL of anhydrous ethanol were added. The mixture was stirred for 60 min, then placed in an autoclave with a polytetrafluoroethylene liner, sealed, and heated at 180 °C for 12 h. After cooling to room temperature, the filtered solid sample was washed twice each with deionized water and anhydrous ethanol, and dried at 60 °C for 12 h to obtain Ag / tBTO nanopowder.

[0076] Experimental Example

[0077] Experimental Example 1

[0078] Transmission electron microscopy (TEM) was performed on Ag / tBTO prepared in Comparative Example 1 and Ag / 0.25F-tBTO prepared in Example 1. The test images are shown below. Figure 1 and Figure 2 As shown.

[0079] Figure 1 (a) and Figure 2 (e) It can be clearly seen that silver nanoparticles with a diameter of 20-30 nm are attached to the surface of tBTO and 0.25F-tBTO.

[0080] Figure 1 (b) Figure 1 (c) and Figure 2 (f) In high-resolution transmission electron microscopy (HRTEM), 0.27 nm belongs to Bi4Ti3O 12 The (200) crystal plane, 0.23 nm, belongs to the (111) crystal plane of elemental silver, combined with Figure 1(a) and Figure 2 (e) confirms that silver nanoparticles are attached to the surfaces of tBTO and 0.25F-tBTO.

[0081] Simultaneously, TEM-EDS mapping scanning was performed on 0.25F-Ag / tBTO, and the test results are as follows: Figure 3 As shown, the test structure confirms that the elements Bi, O, Ti, and F are uniformly distributed, and the presence of Ag nanoparticles can be observed, verifying the presence of elements F and Ag in the compound.

[0082] Experimental Example 2

[0083] X-ray diffraction (XRD) tests were performed on the 0.25F-tBTO and Ag / 0.25F-tBTO prepared in Example 1 and the tBTO and Ag / tBTO prepared in Comparative Example 1. The test results are as follows: Figure 4 As shown.

[0084] Figure 4 The XRD diffraction pattern conforms to Bi4Ti3O 12 The spectrum (JCPDF: 35-0795) shows no other impurity peaks. It can be seen that the diffraction peaks are at their highest intensity (~30°), with the peak intensities of tBTO and Ag / tBTO slightly higher than those of 0.25F-tBTO and Ag / 0.25F-tBTO. This may be because the doping of F slightly reduces the crystallinity of tBTO.

[0085] Experimental Example 3

[0086] Raman spectroscopy was performed on the 0.25F-tBTO and Ag / 0.25F-tBTO prepared in Example 1 and the tBTO and Ag / tBTO prepared in Comparative Example 1. The test results are as follows: Figure 5 As shown.

[0087] like Figure 5 As shown, the peak value at 100-150 nm belongs to the vibrational band of Bi, and the peak value at 250-300 cm⁻¹ belongs to the vibrational band of Bi. -1 The peak value at that location belongs to the [TiO6] octahedral vibration band.

[0088] Experiment Example 4

[0089] The 0.25F-tBTO and Ag / 0.25F-tBTO prepared in Example 1 and the tBTO and Ag / tBTO prepared in Comparative Example 1 were subjected to photocatalytic degradation by methyl orange and methylene blue.

[0090] (1) Add 50 mg of 0.25F-tBTO, Ag / 0.25F-tBTO, tBTO, and Ag / tBTO to 50 mL of 5 mg / L methyl orange solution, respectively, and mix thoroughly to obtain the mixed solution to be degraded. Place the above system in the dark and stir for 30 min.

[0091] Pipette 4 mL of the mixed solution to be degraded into a centrifuge tube, centrifuge for 5 min at 8000 r / min, retain the supernatant and repeat the centrifugation. After centrifugation, take the supernatant and measure the absorbance A0 using a UV spectrophotometer.

[0092] Turn on a 300W xenon lamp and irradiate the mixed solutions to be degraded (containing 0.25F-tBTO, Ag / 0.25F-tBTO, tBTO, and Ag / tBTO, respectively). Then, at regular intervals, take a sample of the degradation solution, centrifuge it according to the steps described above, and measure the absorbance A of the dye. t Record the experimental data and calculate the degradation rate:

[0093] W=C t / C0=A t / A0,

[0094] C t C0 is the concentration of methyl orange solution in the solution at time t under illumination, and A is the initial concentration of methyl orange solution. t is the absorbance of the methyl orange solution at time t under illumination, and A0 is the initial absorbance of the methyl orange solution.

[0095] After the above photocatalytic test, Ag / tBTO and Ag / 0.25F-tBTO were collected by centrifugation, washed with deionized water and ethanol, and centrifuged three times. The collected Ag / tBTO and Ag / 0.25F-tBTO were then dried in an oven at 60℃ for 12 hours. The above degradation steps were repeated three times. The test results of the degradation efficiency changes in the presence of 0.25F-tBTO, Ag / 0.25F-tBTO, tBTO, and Ag / tBTO are as follows. Figure 6 As shown in (a), the fitting curve obtained by fitting the photodegradation kinetics according to the first-order reaction formula ln(C0 / C)=kt is as follows. Figure 6 As shown in (b).

[0096] (2) Degrade a 5 mg / L methylene blue solution using the same method as in (1) for degrading methyl orange solution. The results of the degradation efficiency change test are as follows: Figure 6 As shown in (c), the fitting curve obtained by fitting the photodegradation kinetics according to the first-order reaction formula ln(C0 / C)=kt is as follows. Figure 6 As shown in (d).

[0097] A comparison of the degradation results of methyl orange and methylene blue showed that Ag / tBTO and Ag / 0.25F-tBTO exhibited higher activity than tBTO and 0.25F-tBTO, with Ag / 0.25F-tBTO showing the highest degradation efficiency for pollutants. Specifically... Figure 6 (a) and Figure 6 As shown in (b), tBTO only degraded about 20 wt% of methyl orange after 60 min of continuous illumination, while fluorine doping reduced the degradation rate to 90 wt%. However, Ag / 0.25F-tBTO further improved the degradation rate of methyl orange (to about 97 wt%).

[0098] from Figure 6 (c) and Figure 6 (d) It can be seen that after 40 min of visible light irradiation, the degradation efficiency of methylene blue by Ag / 0.25F-tBTO and Ag / tBTO reached about 95 wt% and 92 wt%, respectively, while the degradation efficiency of methylene blue by tBTO and 0.25F-tBTO was only about 40 wt% and 60 wt%, respectively.

[0099] The photodegradation kinetics were fitted using the first-order reaction formula ln(C0 / C)=kt, and the degradation rate is shown in Table 1. It can be seen that the photocatalytic activity of tBTO is effectively improved after fluorine doping and silver loading due to the synergistic effect of the two.

[0100] Table 1

[0101]

[0102]

[0103] Ag / tBTO and Ag / 0.25F-tBTO were recovered and cyclically degraded for methyl orange and methylene blue under the same reaction conditions. Results are as follows: Figure 7 As shown, the degradation activity of Ag / tBTO and Ag / 0.25F-tBTO catalysts hardly decreased, exhibiting good stability. Figure 7 (a) shows the degradation efficiency curve of methyl orange solution. Figure 7 (b) shows the degradation efficiency curve of methyl orange solution.

[0104] Experimental Example 5

[0105] The photoelectrochemical performance of 0.25F-tBTO and Ag / 0.25F-tBTO prepared in Example 1, and tBTO and Ag / tBTO prepared in Comparative Example 1 were tested. An electrochemical workstation (CHI660E) and a standard three-electrode system were used for photoelectrochemical measurements. An Ag / AgCl electrode and a platinum wire were used as the auxiliary and counter electrodes, respectively. 0.25F-tBTO, Ag / 0.25F-tBTO, tBTO, or Ag / tBTO were used as the working electrode (10 mg of sample was dispersed in 1 mL of ethanol, then dropped onto ITO glass, and dried at room temperature for 12 h to form a uniform film electrode). The electrolyte was 0.1 mol·L⁻¹. -1 Na2SO4 solution, visible light source is 300W Xe lamp.

[0106] Photoelectrochemical measurements were performed using a standard three-electrode system, with electrodes prepared as described above, and irradiated with a 300W xenon lamp. The transient photocurrent response spectrum was obtained, as shown in Figure 8(a).

[0107] Electrochemical impedance spectroscopy (EIS Nyquist curves) was acquired under conditions of AC amplitude of 0.005 V and frequency range of 100 kHz to 0.1 Hz. Figure 8 (b)

[0108] like Figure 8 (a) shows the transient photocurrent response spectra. Under visible light illumination, the photocurrents of 0.25F-tBTO, Ag / 0.25F-tBTO, tBTO, and Ag / tBTO are generated instantaneously upon lamp switching, with the photocurrent intensity in the order Ag / 0.25F-tBTO > Ag / tBTO > 0.25F-tBTO > tBTO. It is generally believed that higher photocurrent density corresponds to lower carrier recombination efficiency and higher photoelectric conversion efficiency. Ag / 0.25F-tBTO exhibits the optimal photocurrent density and the lowest recombination efficiency of photogenerated charge-hole pairs, indicating that the combined effect of F doping and Ag loading improves carrier separation efficiency. Figure 8 (b) It can be seen that the semicircular radii of Ag / tBTO and Ag / 0.25F-tBTO are relatively small, with Ag / 0.25F-tBTO having the smallest radius. This indicates that the loading of silver nanoparticles on the surface of the 0.25F-tBTO catalyst further leads to a decrease in charge transfer resistance. This result suggests that electrons in Ag / 0.25F-tBTO can more easily reach the semiconductor / electrolyte interface for photocatalytic degradation, promoting the degradation of pollutants.

[0109] Experimental Example 6

[0110] The photoluminescence (PL) spectra (fluorescence spectra) of 0.25F-tBTO and Ag / 0.25F-tBTO prepared in Example 1 and tBTO and Ag / tBTO prepared in Comparative Example 1 were measured using a fluorescence spectrometer (PerkinElmer LS55). The room temperature excitation wavelength was 325 nm. The measured fluorescence spectra are shown below. Figure 9 .

[0111] The curve was fitted using a double exponential decay model, and the fitting parameters are shown in Table 2. The formula is τ=∑A i τ i 2 / ∑A i τ i In Table 2, i = 1, 2, τ1 and τ2 represent fluorescence lifetimes, and A1 and A2 represent amplitudes. Compared to tBTO (τ = 3.15 ns) and 0.25F-tBTO (τ = 5.93 ns), the fluorescence lifetimes of Ag / tBTO (τ = 4.87 ns) and Ag / 0.25F-tBTO (τ = 6.66 ns) are extended due to the loading of Ag NPs, as shown in Table 2. Based on the comprehensive analysis of the above electrochemical test results and fluorescence lifetimes, this extension is likely due to the transfer of photogenerated electrons to Ag NPs, thus prolonging the carrier lifetime.

[0112] Table 2

[0113] Photocatalyst <![CDATA[A1]]> <![CDATA[τ1(ns)]]> <![CDATA[A2]]> <![CDATA[τ2(ns)]]> τ(ns) Ag / tBTO 3468.67 4.72 1.42 43.66 4.87 Ag / 0.25F-tBTO 2838.24 6.42 0.97 69.68 6.66

[0114] Experimental Example 7

[0115] The surface potential difference of 0.25F-tBTO and Ag / 0.25F-tBTO prepared in Example 1 and tBTO and Ag / tBTO prepared in Comparative Example 1 were measured using a surface photovoltage spectroscopy (SPV, PL-SPS / IPCE1000). The test results are as follows: Figure 10 As shown.

[0116] The results show that the photovoltaic response of both Ag / tBTO and Ag / 0.25F-tBTO composites is improved compared to tBTO. Loading tBTO and 0.25F-tBTO with silver nanoparticles simultaneously increases the photovoltaic response in both the ultraviolet (300-360 nm) and visible (370-500 nm) regions, with Ag / 0.25F-tBTO exhibiting the largest photovoltage signal. These results indicate that loading Ag nanoparticles can enhance the catalyst's absorption intensity for visible light and improve the separation efficiency of photogenerated carriers, promoting the migration of photogenerated holes to the catalyst surface.

[0117] The present invention has been described in detail above with reference to specific embodiments and / or exemplary examples, as well as the accompanying drawings. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. Use of silver-loaded nanofluorine-doped bismuth titanate, characterized in that, It is used as a photocatalyst to catalyze degradation of organic pollutants; The preparation method of the silver-loaded nanometer fluorine-doped bismuth titanate specifically comprises the following steps: Step 1. Fluorine-doped titanium dioxide is prepared; Step 2. The fluorine-doped titanium dioxide and a bismuth compound are added into a reaction solvent, and high-temperature closed reaction is conducted to obtain nanometer fluorine-doped bismuth titanate; Step 3. The nanometer fluorine-doped bismuth titanate is added into a solvent containing a silver compound, and solvothermal reaction is conducted to obtain silver-loaded nanometer fluorine-doped bismuth titanate, In step 1, the fluorine-doped titanium dioxide is obtained by adding a fluoride and a titanium compound into a solvent, conducting solvothermal reaction, and calcining, wherein the solvothermal reaction temperature is 150-210 DEG C, and the reaction time is 15-28 h; the calcination temperature is 420-480 DEG C, and the calcination time is 2-4 h; In step 3, the solvent is selected from one or more of alcohol solvents, and the solvothermal reaction is conducted in a closed reaction kettle, wherein the reaction temperature is 130-230 DEG C, and the reaction time is 6-18 h.

2. Use according to claim 1, characterized in that, In step 1, The solvothermal reaction temperature is 170-190 DEG C, and the reaction time is 18-24 h; The calcination temperature is 440-460 DEG C, and the calcination time is 2.5-3.5 h.

3. Use according to claim 1, characterized in that, In step 2, the bismuth compound is one or more of bismuth nitrate, bismuth nitrate pentahydrate and bismuth ammonium citrate.

4. Use according to claim 1, characterized in that, In step 3, The silver compound is selected from one or more of silver halide, silver nitrate and silver sulfate; The molar mass ratio of the silver compound to the nanometer fluorine-doped bismuth titanate is 0.01 mmol:(0.2-0.8) g.

5. Use according to claim 4, characterized in that, In step 3, the molar mass ratio of the silver compound to the nanometer fluorine-doped bismuth titanate is 0.01 mmol:(0.3-0.7) g.

6. Use according to claim 5, characterized in that, In step 3, the molar mass ratio of the silver compound to the nanometer fluorine-doped bismuth titanate is 0.01 mmol:(0.4-0.6) g.

7. Use according to claim 3, characterized in that, In step 3, The solvent is selected from one or more of methanol, ethanol, propanol, isopropanol and n-butanol; The volume-mass ratio of the solvent to the nanometer fluorine-doped bismuth titanate is 10 mL:(0.4-0.9) g.

8. Use according to claim 7, characterized in that, In step 3, The solvent is anhydrous ethanol; The volume-mass ratio of the solvent to the nanometer fluorine-doped bismuth titanate is 10 mL:(0.6-0.7) g.

9. Use according to claim 3, characterized in that, In step 3, the reaction temperature is 150-210 DEG C, and the reaction time is 8-16 h.

10. Use according to claim 9, characterized in that, In step 3, the reaction temperature is 170-190 DEG C, and the reaction time is 10-14 h.

11. Use according to claim 1, characterized in that, The fluoride is ammonium fluoride, and the titanium compound is one or more of tetrabutyl titanate, tetraisopropyl titanate and tetraethyl titanate.

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